Breath gas analysis systems and methods

ABSTRACT

Devices and methods are provided for breath gas analysis when determining the difference in the concentrations of at least one gas in the exhaled breathing air on the one hand and in the ambient air on the other hand. The device may include at least one gas sensor, by means of which the concentration of a gas can be determined, and a line system, through whose lines the exhaled air to be examined, the ambient air and a calibrating gas can be selectively pumped to the gas sensor. The method may include feeding ambient air; feeding calibrating gas to the gas sensor; feeding exhaled air to the gas sensor; feeding calibrating gas to the gas sensor again; and feeding exhaled air to the gas sensor again.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/143,350, entitled “BREATH GAS ANALYSIS SYSTEMS AND METHODS,” filedApr. 29, 2016, which claims priority to German Application Serial No.DE102015106949.0, entitled “BREATH GAS ANALYSIS SYSTEMS AND METHODS,”filed May 5, 2015, which are hereby incorporated by reference in theirentirety for all purposes.

TECHNICAL FIELD

The present disclosure generally relates to breath gas analysis and, inparticular, relates to systems and methods for calibrated breath gasanalysis.

BACKGROUND

Devices for breath gas analysis for medical diagnostics or lifestyleapplications have been used for a long time to be able to makestatements regarding the lung function or other body functions of asubject. Methods of this kind are used in particular in the field ofergospirometry. The analysis of the breath gas can provide informationon many metabolic processes of the human body.

SUMMARY

In some scenarios, prior to breath gas analysis using a semiconductordetector, prior to the actual measurement of the breath alcohol content,the semiconductor is calibrated in each case. Breath gas analysisdevices are described, as examples, in DE 20 2009 018 824 U1 and DE 2912 181 C2, which, for example, describe a breath alcohol measuringinstrument having a semiconductor sensor, and both of which are herebyincorporated herein by reference in their entireties.

A calibrating gas may be used for the calibration, which consists ofambient air and a vapor of, for example, one percent alcohol. Once theactual measurement has been completed, the semiconductor sensor ispurged with ambient air to remove all residue of alcohol vapor from themeasuring assembly. It can be of great importance for the validity ofthe breath gas analysis that the gas sensors used for determining theconcentration of a specific gas in the exhaled air are carefullycalibrated. On the one hand, said calibration pertains in particular tozero-point comparison, by which the measuring signal of the gas sensoris calibrated to a specific reference value of the gas concentration tobe determined. On the other hand, said calibration pertains to anamplification of the gas sensor so that a change in the gasconcentration is translated into a proportional change in the measuringsignal of the gas sensor. The present disclosure is concerned, in someaspects, with the zero-point comparison of the gas sensor in breath gasanalyzing devices.

In some breath gas analyzing devices, the gas sensor is calibrated usingambient air and using calibrating gas prior to the beginning of theactual gas analysis on the subject. The ambient air is used to calibratethe gas sensor to a specific zero point because the concentration ofcertain gases in the ambient air is generally very stable and can bereliably predicted with sufficient certainty. Moreover, on average, theambient air contains, for example, 20.9% oxygen and, for example, 0.05%CO2. When calibrating the gas sensor to zero, these gas concentrationsof the ambient air may be taken as a basis. If the ambient air is nowfed through the gas sensor, the measuring signal thus obtained iscalibrated to the gas concentration to be expected in the ambient air.For example, the concentration of oxygen may be calibrated to 20.9%. Inview of the calibration of the amplification of the gas sensor measuringsignal, a breath gas analyzing device may use a calibrating gas, whichis tapped from a gas cylinder, for example.

However, regarding zero-point calibration of the gas sensor, if care isnot taken, there can be measurement errors due to gas sensors beingprone to so-called zero-point fading (sometimes referred to asNullwert-Fading). In other words, this means that the zero point of thegas sensor can change during a measurement because of the technicalproperties of the gas sensor. In some situations, severe measurementerrors may occur if these changes in the zero point are not taken intoaccount. Hence, breath gas analyzing devices may be provided thatrecalibrate the zero point at regular intervals also during ameasurement.

In the course of this zero-point calibration, ambient air may be fed tothe gas sensor instead of the exhaled air to be analyzed so as torecalibrate the gas sensor to the correspondingly known gasconcentration value of the ambient air. A pneumatic switch valve may beused for switching from exhaled air to ambient air. It can be importantfor the accuracy of a breath gas analyzing device to observe the changesin gas concentration at the suction point as precisely as possible. Inparticular, at the beginning and at the end of the exhalation, thesechanges in gas concentration can occur very suddenly. Because of the gaspath, there is the risk that the changes in gas concentration may weakenand thus become distorted. Complex gas paths with poorly purged volumes,as they are often found in pneumatic valves, pose an increased risk inthis case.

Therefore, according to various embodiments, a method for operating anew device is provided for breath gas analysis when determining thedifference in the concentrations of at least one gas in the exhaledbreathing air and in the ambient air, by means of which the complexityof the device and the potential distortion of the changes in gasconcentration due to the pneumatic valve system during the actual breathgas analysis can be reduced.

In one embodiment, the above object is attained by a method foroperating a device for breath gas analysis when determining thedifference in the concentrations of at least one gas in the exhaledbreathing air and in the ambient air, the device including at least onegas sensor, by means of which the concentration of a gas can bedetermined, and including a line system, through whose lines the exhaledair to be examined, the ambient air and a calibrating gas can beselectively pumped to the gas sensor, the method including: (a) feedingambient air to the gas sensor and determining the gas concentration inthe ambient air, the output signal of the gas sensor being temporarilystored as an ambient air reference value; (b) feeding calibrating gas tothe gas sensor, the calibrating gas being fed to the gas sensor alongthe same common line path as the exhaled air and the ambient air withinthe device, and determining the gas concentration in the calibratinggas, the output signal of the gas sensor being temporarily stored as acalibrating gas reference value; (c) feeding exhaled air to the gassensor and determining the gas concentration in the exhaled air, theoutput signal of the gas sensor being temporarily stored as a measuredvalue so as to determine the difference in the gas concentration in theexhaled air on the one hand and in the ambient air on the other handusing the ambient air reference value; (d) feeding calibrating gas tothe gas sensor and determining the gas concentration in the calibratinggas, the output signal of the gas sensor being compared to thecalibrating gas reference value and the difference being temporarilystored as a correction value; and (e) feeding exhaled air to the gassensor and determining the gas concentration in the exhaled air, theoutput signal of the gas sensor being temporarily stored as a measuredvalue so as to determine the difference in the gas concentration in theexhaled air on the one hand and in the ambient air on the other handusing the ambient air reference value and the correction value.

According to another embodiment, a method is provided that includes:feeding ambient air to a gas sensor along a line path of a gas analysisdevice; determining a first gas concentration in the ambient air withthe gas sensor; storing a first output signal of the gas sensortemporarily as an ambient air reference value; feeding calibrating gasto the gas sensor, the calibrating gas being fed to the gas sensor alongthe same common line path as the ambient air; determining a second gasconcentration in the calibrating gas with the gas sensor; storing asecond output signal of the gas sensor temporarily as a calibrating gasreference value; feeding exhaled air to the gas sensor along the samecommon line path; determining a third gas concentration in the exhaledair with the gas sensor; storing a third output signal of the gas sensortemporarily as a measured value; determining a difference between thethird gas concentration in the exhaled air and the first gasconcentration in the ambient air using the ambient air reference value;feeding additional calibrating gas to the gas sensor along the samecommon line path; determining a fourth gas concentration in theadditional calibrating gas; storing a fourth output signal of the gassensor corresponding to the fourth gas concentration; comparing thefourth output signal to the calibrating gas reference value; storing adifference between the fourth output signal and the calibration gasreference value temporarily as a correction value; feeding additionalexhaled air to the gas sensor along the same common line path;determining a fifth gas concentration in the additional exhaled air withthe gas sensor; storing a fifth output signal of the gas sensortemporarily as an additional measured value; and determining a seconddifference between the fifth gas concentration in the additional exhaledair and the first gas concentration in the ambient air using the ambientair reference value and the correction value.

According to another embodiment, a device for breath gas analysis isprovided, the device including: a first intake, external to the device,for exhaled air from a subject and for ambient air; a first line pathfor the exhaled air and the ambient air, the line path extending fromthe first intake into the device; at least one gas sensor disposedwithin the device along the line path; a second intake, external to thedevice, for a calibration gas; and a second line path extending from thesecond intake to a portion of the first line path, the portion disposedexternal to the device such that the second intake is fluidly coupled tothe at least one gas sensor via the second line path and the first linepath.

According to another embodiment, a method is provided that includes:providing ambient air along a line path of a gas analysis device to agas sensor disposed within the device; providing exhaled air from asubject along the same line path to the gas sensor; and providing acalibration gas along the same line path to the gas sensor while theline path is open to the ambient air or the exhaled air.

In in a first step of a method according to an embodiment, ambient airis fed to the gas sensor to determine the gas concentration in theambient air. The output signal of the gas sensor thus obtained isassociated with the gas concentration known per se of the correspondinggas in the ambient air, such as 20.9% oxygen, and is temporarily storedas an ambient air reference value.

Subsequently, according to various embodiments, a calibrating gas is fedto the sensor, said calibrating gas also containing a gas of thecorresponding sort, such as oxygen. The gas concentration of this gas inthe calibrating gas is determined by the gas sensor, too, and thecorresponding output signal of the gas sensor is temporarily stored as acalibrating gas reference value.

In the next step, according to various embodiments, the actual breathgas analysis begins. To this end, the subject is connected to the linesystem of the device, for example by means of a correspondingly suitablemouthpiece, and the exhaled air of the subject is fed to the gas sensor.Using the reference values stored in the device, in particular using theambient air reference value determined in operation (a) noted above, thedifference in the gas concentrations in the exhaled air on the one handand in the ambient air on the other hand is determined.

At some point a shift of the measurement characteristic of the gassensor may occur, such as after a certain measuring time has elapsed.Thus, according to various embodiments, no ambient air is fed to the gassensor to recalibrate the gas sensor. Instead, the calibrating gaspreviously used in operation (b) above is fed to the gas sensor againand the gas concentration of the corresponding gas in the calibratinggas is determined. The output signal of the gas sensor thus obtained issubsequently compared to the calibrating gas reference value previouslydetermined in operation (b), for example. The difference thus obtainedbetween the measuring signals may be regarded as the degree of thechange in the measurement characteristic of the gas sensor. If thedifference is close to zero, the measured-value characteristic of thegas sensor has not changed. The measured-value difference obtained inthis step is stored in the evaluating device as a correction value.

Subsequently, according to various embodiments, the actual breath gasanalysis is continued and exhaled air is fed to the gas sensor again forthis purpose. The output signal of the gas sensor thus obtained istemporarily stored as a measured value and is evaluated in theevaluating device to determine the gas concentration in the exhaled air.The evaluation takes place using the ambient air reference value and thecorrection value. Thus, in various embodiments, the zero-pointcalibration may be repeatedly performed at certain intervals during theactual breath gas analysis, and may be performed not using ambient air,but using calibrating gas. In this way, a more accurate calibration maybe performed, because a change in the measurement characteristic of thegas sensor is significantly characterized by the difference thusobtained between the calibrating gas reference value and the measuringsignal of the gas sensor determined later by feeding of the calibratinggas. When the breath gas analysis is evaluated later, the correctingvalue thus obtained can be used to correct the ambient air referencevalue so as to avoid measurement errors that are caused by the change inthe measurement characteristic of the gas sensor. For example, if acorrecting value of 10% is obtained, this means that the gas sensormeasures the gas composition of the calibrating gas with ameasured-value characteristic that is changed by 10%. This change canthen be proportionally applied to the ambient air reference value. Byusing the calibrating gas instead of the ambient air during zero-pointrecalibration, the complexity of the device can be reduced because thepreviously known valve systems for feeding the ambient air to the gassensor are unnecessary during the actual breath gas analysis. At thesame time, this omission of the valve system reduces the risk ofdistortion of the quick changes in gas concentration.

The measurement characteristic of gas sensors in breath gas analyzingdevices can be highly sensitive to different pressure drops and/orchanges of the gas flow velocity in the line paths used, via which thegas to be analyzed is fed to the gas sensor. If the calibrating gas andthe exhaled air are fed to the gas sensor along different line paths,the resulting pressure-drop difference and/or changes of the gas flowvelocity can cause a definitely relevant measurement error.

To preclude said measurement error in a simple manner, it is providedaccording to the present disclosure that the calibrating gas is fed tothe gas sensor along the same common line path within the device as theexhaled air and the ambient air when determining the calibrating gasreference value and when determining the correction value later. As aresult, it is achieved that there is the same pressure drop and the samegas flow velocity in each line path used during all gas analyses, namelyduring analysis of the gas concentration in the exhaled air, in theambient air and in the calibrating gas, and differences and theresulting measurement errors are correspondingly avoided.

If calibrating gas is pumped to the gas sensor during the actual breathgas analysis to recalibrate the zero point of the gas sensor, the systemmay be operated to ensure that, prior to the actual determination of thecorrection value, the exhaled air is substantially completely displacedfrom the area of the gas sensor and from the upstream line paths. Torealize this displacement in a simple manner, the calibrating gas can bepumped with a pumping capacity that is higher than the pumping capacityfor pumping the breathing or ambient air through the device. Thedifference in pumping capacity with a higher pumping capacity forfeeding the calibrating gas allows the calibrating gas to displace theexhaled air or the ambient air from the line paths toward the gas sensorand thus from the gas sensor itself without any other technical measuresand while the line path remains open to the breathing air source or tothe ambient air source. This is because, based on the higher pumpingcapacity, the corresponding line paths and thus the gas sensor arepurged with the calibrating gas and there is no longer a way for theexhaled air or ambient air to reach the gas sensor despite the open linepath.

In view of a simplified technical structure of the breath gas analyzingdevice, it may be desirable for the calibrating gas to be pumped from apressurized gas cylinder into the line path toward the gas sensor. Thus,based on the pressure of the calibrating gas in the gas cylinder, aseparate pumping device such as a feed pump for pumping the calibratinggas may be omitted in some embodiments.

If the calibrating gas is pumped through the device from a gas cylinderby means of pressure, the calibrating gas can preferably flow through atleast one pressure throttle so as to correspondingly stabilize thepressure of the calibrating gas. However, a feed pump may be providedfor pumping the exhaled air or the ambient air through the breath gasanalyzing device.

To avoid variations of the changes in gas concentration, the feed pumpmay be connected downstream of the gas sensor so that the exhaled air orthe ambient air is sucked through the gas sensor by the feed pump.

According to some embodiments, described is a valve that may be openedbetween the calibrating gas source, such as a pressurized gas cylinder,and the common line path when the calibrating gas is fed into the commonline path. Because of the pressure in the calibrating gas source, thecalibrating gas flows into the common line path when the valve isopened. At the same time, the line path toward the breathing air sourceor toward the ambient air source stays open as well, making the use ofadditional check valves expendable. The pumping capacity caused by thepressure of the calibrating gas in the common line path is higher thanthe pumping capacity caused by the feed pump so that the calibrating gasdisplaces the exhaled air or the ambient air from the common line pathin the shortest time because of the difference in pumping capacity.

The feeding capacities at which the calibrating gas on the one hand andthe exhaled air or the ambient air on the other hand are fed through thedevice are generally optional. A pumping capacity of 310 mL/min for thecalibrating gas and of about 210 mL/min for the exhaled air or ambientair has proved especially suitable. The difference in pumping capacityof about 100 mL/min realizes an effective and resource-savingdisplacement of the exhaled air or ambient air by the calibrating gas.

To avoid the introduction of liquid droplets into the gas sensor, apurging vessel may be provided along the common line path in whichliquid droplets are gravimetrically removed from the analyzed airstream.

Which gas concentrations are determined by the method according to theinvention is also optional in general. The determination of theconcentration of oxygen and the determination of the concentration ofcarbon dioxide are described herein as examples.

In summary, it is to be noted that the individual method steps of themeasuring method according to the disclosure can of course besupplemented by additional intermediate steps. The individual methodsteps of the method according to the invention do not necessarily haveto be performed successively without any intermediate steps. Instead, itis characteristic for the method according to the disclosure that theindividual steps of the method according to the invention are performedwithout relying on the performance of additional intermediate stepsbetween the individual stages of the method.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide furtherunderstanding and are incorporated in and constitute a part of thisspecification, illustrate disclosed embodiments and together with thedescription serve to explain the principles of the disclosedembodiments. In the drawings:

FIG. 1 is a diagram of a breath gas analyzing device during breath gasanalysis in a schematic view according to certain aspects of the presentdisclosure.

FIG. 2 illustrates a schematic illustration of a measurement diagramduring determination of gas concentrations for breath gas analysisaccording to certain aspects of the present disclosure.

FIG. 3 illustrates a schematic diagram of a breath gas analyzing deviceduring a first operation of a breath gas analysis according to certainaspects of the present disclosure.

FIG. 4 illustrates a schematic diagram of the breath gas analyzingdevice of FIG. 3 during a subsequent operation of the breath gasanalysis according to certain aspects of the present disclosure.

FIG. 5 illustrates a schematic diagram of the breath gas analyzingdevice of FIG. 3 during another subsequent operation of the breath gasanalysis according to certain aspects of the present disclosure.

FIG. 6 illustrates a schematic diagram of the breath gas analyzingdevice of FIG. 3 during another subsequent operation of the breath gasanalysis according to certain aspects of the present disclosure.

FIG. 7 illustrates a schematic diagram of the breath gas analyzingdevice of FIG. 3 during another subsequent operation of the breath gasanalysis according to certain aspects of the present disclosure.

FIGS. 8A and 8B illustrate a flow chart of operations that may beperformed for breath gas analysis according to certain aspects of thepresent disclosure.

DETAILED DESCRIPTION

The detailed description set forth below describes variousconfigurations of the subject technology and is not intended torepresent the only configurations in which the subject technology may bepracticed. The detailed description includes specific details for thepurpose of providing a thorough understanding of the subject technology.Accordingly, dimensions may be provided in regard to certain aspects asnon-limiting examples. However, it will be apparent to those skilled inthe art that the subject technology may be practiced without thesespecific details. In some instances, well-known structures andcomponents are shown in block diagram form in order to avoid obscuringthe concepts of the subject technology.

It is to be understood that the present disclosure includes examples ofthe subject technology and does not limit the scope of the appendedclaims. Various aspects of the subject technology will now be disclosedaccording to particular but non-limiting examples. Various embodimentsdescribed in the present disclosure may be carried out in different waysand variations, and in accordance with a desired application orimplementation.

In the following detailed description, numerous specific details are setforth to provide a full understanding of the present disclosure. It willbe apparent, however, to one ordinarily skilled in the art thatembodiments of the present disclosure may be practiced without some ofthe specific details. In other instances, well-known structures andtechniques have not been shown in detail so as not to obscure thedisclosure.

FIG. 1 shows a device 01 for breath gas analysis, by means of which thegas concentration of oxygen and carbon dioxide in the exhaled breathingair of a subject can be measured, for example. In the example of FIG. 1,the subject 02 is connected to the line system of the device 01 by meansof a suitable patient connection means, such as a mouthpiece 03 or amask (with and without check valves) or a tube system, and the exhaledair is fed to the gas sensors 04 and 05 via the line system. Byevaluating the measuring signals of the gas sensor 04, the carbondioxide content can be determined, and by evaluating the measuringsignals of the gas sensor 05, the oxygen content in the exhaled air canbe determined. The exhaled air is pumped through the line system of thedevice 01 by means of a feed pump 06.

To calibrate the gas sensors 04 and 05 to a known reference value (zeropoint) at the beginning of the actual breath gas analysis, ambient airis suctioned from the surroundings via the empty mouthpiece 03 and fedto the gas sensors 04 and 05 before the subject 02 is connected to thedevice. The measuring signal of the CO2 gas sensor 04 thus obtained iscalibrated to the ambient air reference value of 0.05% CO2 in theambient air. The 02 gas sensor 05 is calibrated to the ambient airreference value of 20.9% oxygen.

To calibrate the measured-value amplification of the two gas sensors 04and 05, a calibrating gas is subsequently fed from a gas cylinder 07through the line system of the device 01 to the gas sensors 04 and 05 byswitching the valve 10, and a corresponding amplification calibration isperformed.

Since the measurement characteristic of the gas sensors 04 and 05 oftenchanges in an undesired manner during the actual breath gas analysisbecause of so-called zero-point fading, it is provided with the device01 that ambient air may again be fed to the gas sensors 04 and 05 atcertain intervals for the purpose of zero-point calibration. To thisend, the ambient air 08 can be suctioned in via another line path byswitching the valve 09 and can be fed to the gas sensors 04 and 05 whilethe subject 02 is connected to the device 01. However, in the example ofFIG. 1, the ambient air 08 will reach the gas sensors 04 and 05 alonganother line path than the breathing air during the actual breath gasanalysis, which may lead to measurement errors. Moreover, the additionalzero-point calibration during the actual breath gas analysis may bedisadvantageous because the breath gas analysis is thus prolonged in anundesired manner.

FIG. 2 shows a schematically illustrated measurement diagram of a systemfor performing the methods according to the invention using a breath gasanalyzing device 320 as shown in FIG. 3. As an example, the measuringsignal Y of the gas sensor 305 for determining the oxygen concentrationis marked over time. The illustration is schematic and serves toexemplify the systems, methods, and devices according to the presentdisclosure.

During a first operation, in the time between t0 and t1, the subject isnot yet connected to the device 320 and ambient air 308 is pumped to thegas sensors 304 and 305 (e.g., an oxygen sensor and a carbon dioxidesensor) by, for example, being driven by the feed pump 306. Themeasuring signal 11 thus obtained, which with regard to oxygen, may (forexample) correspond to a gas concentration of 20.9% oxygen, is stored asan ambient air reference value.

As schematically illustrated in FIG. 4, calibrating gas may be fed fromthe gas cylinder 307 (as indicated by arrow 400) through the line systemof the device 320 to the gas sensors 304 and 305 by, for example,switching the valve 310. The calibrating gas may flow in at a pumpingcapacity of 310 mL/min, thus displacing the ambient air that is locatedin the line system and is fed at lower pumping capacity (e.g., a pumpingcapacity of only 210 mL/min) by the feed pump 306. Once the ambient airis completely displaced, the measuring signal 12, which (for example)corresponds to the oxygen concentration in the calibrating gas, issubsequently temporarily stored as a calibrating gas reference value inthe time between t1 and t2 (FIG. 2).

In a subsequent operation, as illustrated in the configuration of device320 in FIG. 5, the subject 502 is connected to the device 503 (e.g., amouthpiece attached to the intake) and the valve 310 is closed. In thisway, the breathing air exhaled by the subject 502 (e.g., in thedirection of arrow 504) now flows through the line system to the gassensors 304 and 305. The gas concentration of oxygen can be exactlydetermined by evaluating the measuring signal 13 (FIG. 2) relative tothe previously determined ambient air reference value. As shown in FIGS.3-5, the ambient air and the exhaled air may flow from a first intakeexternal to the device 320 along a first line path to the gas sensors304 and/or 305 disposed within the device. The first line path mayextend from the first intake external to the device to the gas sensor.The calibrating gas may flow along a second line path from a secondintake external to the device for the calibrating gas. The second linepath may extend from the second intake to a portion of the first linepath that is disposed, for example, external to the device. The secondline path may fluidly couple to the first line path at a locationadjacent to the first intake (e.g., external to the device) so thatcalibration (calibration) gas is provided to the gas sensors along thesame first line path as the ambient air and the exhaled air. Althoughthe first and second line paths are shown converging at a locationoutside the device, this is merely illustrative. In other embodiments,the first and second line paths may converge at a location interior tothe device and adjacent to the intake for exhaled and ambient air suchthat the calibration gas is provided to the gas sensor(s) along the samefirst line path as the ambient and/or exhaled air.

Valve 310 may be disposed on the second line path between the secondintake and the portion of the first line path. Feed pump 306 may bedisposed downstream of the gas sensors. Optional purge device 317 may bedisposed on the first line path between the first intake and the gassensors.

After a certain measuring period, a zero-point recalibration may beperformed to be able to correct measurement errors by way of a changedmeasurement characteristic of the gas sensors 304 and 305. The subject502 stays connected to the device 320 in the meantime. However, asindicated in FIG. 6, the valve 310 is opened and the calibrating gasflows from the gas cylinder 307 (as indicated by arrow 600) through theline system at a pumping capacity of, for example, 310 mL/min anddisplaces the exhaled air. Once the exhaled air has been substantiallycompletely displaced, the gas concentration of, for example, oxygen inthe reference gas is measured again in the time period between t3 and t4(FIG. 2). The measuring signal 14 thus obtained is compared to thecalibrating gas reference value and the difference 15 is stored in theevaluating device. The difference value 15 represents a degree of thechange in the measurement characteristic of the gas sensor 305 and canbe used to correct errors when evaluating the subsequent measurements.

Finally, as illustrated in the configuration shown in FIG. 7, theexhaled air of the subject 502 may again be fed (e.g., in the directionof arrow 700) to the gas sensors 304 and 305 by closing the valve 310and by operating the feed pump 306. When evaluating the resultingmeasuring signal 16 (FIG. 2) of the gas sensor 305, the correction value15 is then taken into account as an additional value (e.g., to determinea corrected ambient air value 11 a to which the measuring value 13 canbe compared). The type of correction method to be selected for thispurpose is to be selected according to the analyzing characteristic. Theoffset adjustment illustrated in FIG. 2 is to be understood as anexample and does not limit the disclosure in its core.

An optional purging vessel 317 may be provided that serves to removeliquid droplets in the exhaled air. Additional method steps oroperations may take place between the individual method steps describedabove. These steps, such as steps for displacing the gases following oneanother, are not illustrated in FIG. 2.

Illustrative operations that may be performed for calibrated breath gasanalysis using, for example, the system of FIGS. 2-7, are shown in FIGS.8A and 8B, according to an embodiment.

At block 800, ambient air may be fed to a gas sensor along a line path.

At block 802, a gas concentration in the ambient air may be determinedwith the gas sensor.

At block 804, the output signal of the gas sensor (e.g., a measurementvalue of the determined gas concentration in the ambient air) may bestored, at least temporarily, as an ambient air reference value.

At block 806, a calibrating gas may be fed to the gas sensor. Thecalibrating gas may be fed to the gas sensor along the same common linepath as the ambient air within the device.

At block 808, the gas concentration in the calibrating gas may bedetermined with the gas sensor.

At block 810, the output signal of the gas sensor (e.g., a measurementvalue of the determined gas concentration in the calibrating gas) may bestored, at least temporarily, as a calibrating gas reference value.

At block 812, exhaled air (e.g., from a subject) may be fed to the gassensor along the same line path.

At block 814, the gas concentration in the exhaled air may be determinedwith the gas sensor.

At block 816, the output signal of the gas sensor (e.g., a measurementvalue of the determined gas concentration in the exhaled air) may bestored, at least temporarily, as a measured value.

At block 818, the difference in the gas concentration in the exhaled airand the gas concentration in the ambient air may be determined using theambient air reference value.

At block 820, additional calibrating gas may be fed to the gas sensor.The additional calibrating gas may be fed to the gas sensor along thesame common line path as the ambient air within the device. Thecalibrating gas may be provided to the same common line path from anadditional, second line path extending from an intake for thecalibration gas to the first line path. Providing the calibrating gasand/or the additional calibrating gas may include operating a valve onthe second line path to allow the calibrating gas to flow to the firstline path.

At block 822, the gas concentration in the additional calibrating gasmay be determined with the gas sensor.

At block 824, the output signal of the gas sensor (e.g., the gasconcentration in the additional calibrating gas) may be compared to thecalibrating gas reference value.

At block 826, the difference between the output signal of the gas sensor(e.g., the gas concentration in the additional calibrating gas) and thecalibrating gas reference value may be stored, at least temporarily, asa correction value.

At block 828, additional exhaled air may be fed (e.g., from the samesubject) to the gas sensor along the line path.

At block 830, the gas concentration in the additional exhaled air may bedetermined with the gas sensor.

At block 832, the output signal of the gas sensor (e.g., the gasconcentration in the additional exhaled air) may be stored, at leasttemporarily, as a measured value (e.g., an additional measured value forthe additional exhaled air).

At block 834, the difference in the gas concentration in the exhaled air(and/or the additional exhaled air) and in the ambient air may bedetermined using the ambient air reference value and the correctionvalue.

The subject technology is illustrated, for example, according to variousaspects described above. Various examples of these aspects are describedas numbered concepts or clauses (1, 2, 3, etc.) for convenience. Theseconcepts or clauses are provided as examples and do not limit thesubject technology. It is noted that any of the dependent concepts maybe combined in any combination with each other or one or more otherindependent concepts, to form an independent concept. The following is anon-limiting summary of some concepts presented herein:

Concept 1. A method, comprising:

feeding ambient air to a gas sensor along a line path of a gas analysisdevice;

determining a first gas concentration in the ambient air with the gassensor;

storing a first output signal of the gas sensor temporarily as anambient air reference value;

feeding calibrating gas to the gas sensor, the calibrating gas being fedto the gas sensor along the same common line path as the ambient air;

determining a second gas concentration in the calibrating gas with thegas sensor; storing a second output signal of the gas sensor temporarilyas a calibrating gas reference value;

feeding exhaled air to the gas sensor along the same common line path;

determining a third gas concentration in the exhaled air with the gassensor;

storing a third output signal of the gas sensor temporarily as ameasured value; determining a difference between the third gasconcentration in the exhaled air and the first gas concentration in theambient air using the ambient air reference value;

feeding additional calibrating gas to the gas sensor along the samecommon line path;

determining a fourth gas concentration in the additional calibratinggas;

storing a fourth output signal of the gas sensor corresponding to thefourth gas concentration;

comparing the fourth output signal to the calibrating gas referencevalue;

storing a difference between the fourth output signal and thecalibration gas reference value temporarily as a correction value;

feeding additional exhaled air to the gas sensor along the same commonline path;

determining a fifth gas concentration in the additional exhaled air withthe gas sensor;

storing a fifth output signal of the gas sensor temporarily as anadditional measured value; and

determining a second difference between the fifth gas concentration inthe additional exhaled air and the first gas concentration in theambient air using the ambient air reference value and the correctionvalue.

Concept 2. The method according to Concept 1 or any other Concept,wherein, while the calibrating gas is fed into the common line path,said common line path stays open toward a breathing air source of theexhaled air and/or an ambient air source, the calibrating gas beingpumped into the common line path at a higher pumping capacity than theexhaled air and/or the ambient air, and the exhaled air and/or theambient air being displaced from the common line path by the calibratinggas because of the difference in pumping capacity.

Concept 3. The method according to Concept 1 or any other Concept,wherein the calibrating gas is pumped into the common line path from apressurized gas cylinder.

Concept 4. The method according to Concept 3 or any other Concept,wherein the calibrating gas flows through at least one pressurethrottle.

Concept 5. The method according to Concept 1 or any other Concept,wherein the exhaled air and the ambient air are pumped into the commonline path by being driven by a feed pump.

Concept 6. The method according to Concept 5 or any other Concept,wherein the exhaled air and the ambient air are pumped through thecommon line path by a vacuum generated by the feed pump downstream ofthe gas sensor.

Concept 7. The method according to Concept 5 or any other Concept,wherein, when the calibrating gas is fed into the common line path, avalve between a source of the calibrating gas and the common line pathis opened, the common line path staying open toward a breathing airsource of the exhaled air or an ambient air source, and a pumpingcapacity generated in the common line path by a pressure of thecalibrating gas being higher than a pumping capacity caused by the feedpump.

Concept 8. The method according to Concept 7 or any other Concept,wherein the calibrating gas is pumped by a pressure at a pumpingcapacity of about 310 mL/min and the exhaled air or the ambient air ispumped into the common line path at a pumping capacity of about 210mL/min by being driven by the feed pump.

Concept 9. The method according to Concept 1 or any other Concept,wherein a purging vessel is provided along the common line path, theexhaled air flowing through said purging vessel and liquid dropletsbeing removed from the exhaled air.

Concept 10. The method according to any one of Concept 1 or any otherConcept, further comprising, determining, with the gas sensor, aconcentration of oxygen in the exhaled air.

Concept 11. The method according to Concept 1 or any other Concept,further comprising, determining, with the gas sensor, a concentration ofcarbon dioxide in the exhaled air.

Concept 12. A device for breath gas analysis, the device comprising:

a first intake, external to the device, for exhaled air from a subjectand for ambient air;

a first line path for the exhaled air and the ambient air, the line pathextending from the first intake into the device;

at least one gas sensor disposed within the device along the line path;a second intake, external to the device, for a calibration gas; and

a second line path extending from the second intake to a portion of thefirst line path, the portion disposed external to the device such thatthe second intake is fluidly coupled to the at least one gas sensor viathe second line path and the first line path.

Concept 13. The device of Concept 12 or any other Concept, furthercomprising a valve on the second line path between the second intake andthe portion of the first line path.

Concept 14. The device of Concept 13 or any other Concept, furthercomprising a feed pump configured to pump the exhaled air and theambient air from the first intake to the at least one gas sensor.

Concept 15. The device of Concept 14 or any other Concept, wherein thefeed pump is connected downstream of the at least one gas sensor toconfigured the feed pump to suck the exhaled air and the ambient air isthrough the at least one gas sensor.

Concept 16. The device of Concept 15 or any other Concept, wherein theat least one gas sensor comprises two gas sensors.

Concept 17. The device of Concept 16 or any other Concept, wherein thetwo gas sensor comprise an oxygen sensor and a carbon dioxide sensor.

Concept 18. The device of Concept 14 or any other Concept, furthercomprising a purging vessel on the first line path between the firstintake and the at least one gas sensor.

Concept 19. The device of Concept 12 or any other Concept, furthercomprising a calibration gas container coupled to the second intake andcontaining compressed calibration gas.

Concept 20. A method, comprising:

providing ambient air along a line path of a gas analysis device to agas sensor disposed within the device;

providing exhaled air from a subject along the same line path to the gassensor; and

providing a calibration gas along the same line path to the gas sensorwhile the line path is open to the ambient air or the exhaled air.

The present disclosure is provided to enable any person skilled in theart to practice the various aspects described herein. The disclosureprovides various examples of the subject technology, and the subjecttechnology is not limited to these examples. Various modifications tothese aspects will be readily apparent to those skilled in the art, andthe generic principles defined herein may be applied to other aspects.

A reference to an element in the singular is not intended to mean “oneand only one” unless specifically so stated, but rather “one or more.”Unless specifically stated otherwise, the term “some” refers to one ormore. Pronouns in the masculine (e.g., his) include the feminine andneuter gender (e.g., her and its) and vice versa. Headings andsubheadings, if any, are used for convenience only and do not limit theinvention.

The word “exemplary” is used herein to mean “serving as an example orillustration.” Any aspect or design described herein as “exemplary” isnot necessarily to be construed as preferred or advantageous over otheraspects or designs. In one aspect, various alternative configurationsand operations described herein may be considered to be at leastequivalent.

As used herein, the phrase “at least one of” preceding a series ofitems, with the term “or” to separate any of the items, modifies thelist as a whole, rather than each item of the list. The phrase “at leastone of” does not require selection of at least one item; rather, thephrase allows a meaning that includes at least one of any one of theitems, and/or at least one of any combination of the items, and/or atleast one of each of the items. By way of example, the phrase “at leastone of A, B, or C” may refer to: only A, only B, or only C; or anycombination of A, B, and C.

A phrase such as an “aspect” does not imply that such aspect isessential to the subject technology or that such aspect applies to allconfigurations of the subject technology. A disclosure relating to anaspect may apply to all configurations, or one or more configurations.An aspect may provide one or more examples. A phrase such as an aspectmay refer to one or more aspects and vice versa. A phrase such as an“embodiment” does not imply that such embodiment is essential to thesubject technology or that such embodiment applies to all configurationsof the subject technology. A disclosure relating to an embodiment mayapply to all embodiments, or one or more embodiments. An embodiment mayprovide one or more examples. A phrase such an embodiment may refer toone or more embodiments and vice versa. A phrase such as a“configuration” does not imply that such configuration is essential tothe subject technology or that such configuration applies to allconfigurations of the subject technology. A disclosure relating to aconfiguration may apply to all configurations, or one or moreconfigurations. A configuration may provide one or more examples. Aphrase such a configuration may refer to one or more configurations andvice versa.

In one aspect, unless otherwise stated, all measurements, values,ratings, positions, magnitudes, sizes, and other specifications that areset forth in this specification, including in the claims that follow,are approximate, not exact. In one aspect, they are intended to have areasonable range that is consistent with the functions to which theyrelate and with what is customary in the art to which they pertain.

It is understood that the specific order or hierarchy of steps, oroperations in the processes or methods disclosed are illustrations ofexemplary approaches. Based upon implementation preferences orscenarios, it is understood that the specific order or hierarchy ofsteps, operations or processes may be rearranged. Some of the steps,operations or processes may be performed simultaneously. In someimplementation preferences or scenarios, certain operations may or maynot be performed. Some or all of the steps, operations, or processes maybe performed automatically, without the intervention of a user. Theaccompanying method claims present elements of the various steps,operations or processes in a sample order, and are not meant to belimited to the specific order or hierarchy presented. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed under the provisions of 35U.S.C. § 112 (f) unless the element is expressly recited using thephrase “means for” or, in the case of a method claim, the element isrecited using the phrase “step for.” Furthermore, to the extent that theterm “include,” “have,” or the like is used, such term is intended to beinclusive in a manner similar to the term “comprise” as “comprise” isinterpreted when employed as a transitional word in a claim.

The Title, Background, Summary, Brief Description of the Drawings andAbstract of the disclosure are hereby incorporated into the disclosureand are provided as illustrative examples of the disclosure, not asrestrictive descriptions. It is submitted with the understanding thatthey will not be used to limit the scope or meaning of the claims. Inaddition, in the Detailed Description, it can be seen that thedescription provides illustrative examples and the various features aregrouped together in various embodiments for the purpose of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed subject matter requires morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter lies in less than allfeatures of a single disclosed configuration or operation. The followingclaims are hereby incorporated into the Detailed Description, with eachclaim standing on its own as a separately claimed subject matter.

The claims are not intended to be limited to the aspects describedherein, but are to be accorded the full scope consistent with thelanguage of the claims and to encompass all legal equivalents.Notwithstanding, none of the claims are intended to embrace subjectmatter that fails to satisfy the requirement of 35 U.S.C. § 101, 102, or103, nor should they be interpreted in such a way.

What is claimed:
 1. A method, comprising: determining, by a gas sensor,a first gas concentration in ambient air; determining an ambient airreference value based on the first gas concentration; determining, bythe gas sensor, a second gas concentration in a calibrating gas;determining a calibrating gas reference value based on the second gasconcentration; determining, by the gas sensor, a third gas concentrationin exhaled air; determining a measured value based on the third gasconcentration; determining, by the gas sensor, a fourth gasconcentration in additional calibrating gas; determining a correctionvalue based on a difference between the fourth gas concentration and thecalibration gas reference value; determining a corrected ambient airreference value based on the correction value; determining, by the gassensor, a fifth gas concentration in additional exhaled air; andperforming a breath gas analysis of the fifth gas concentration usingthe corrected ambient air reference value.
 2. The method according toclaim 1, wherein the ambient air, the calibrating gas and the exhaledair are fed to the sensor via a common line path.
 3. The methodaccording to claim 2, wherein, while the calibrating gas is fed into thecommon line path, said common line path stays open toward an ambient airsource, the calibrating gas being pumped into the common line path at ahigher pumping capacity than the ambient air, and the ambient air beingdisplaced from the common line path by the calibrating gas because ofthe difference in pumping capacity.
 4. The method according to claim 2,wherein the calibrating gas is pumped into the common line path from apressurized gas cylinder.
 5. The method according to claim 4, whereinthe calibrating gas flows through at least one pressure throttle.
 6. Themethod according to claim 2, wherein the exhaled air and the ambient airare pumped into the common line path by being driven by a feed pump. 7.The method according to claim 6, wherein the exhaled air and the ambientair are pumped through the common line path by a vacuum generated by thefeed pump downstream of the gas sensor.
 8. The method according to claim6, wherein, when the calibrating gas is fed into the common line path, avalve between a source of the calibrating gas and the common line pathis opened, the common line path staying open toward a breathing airsource of the exhaled air or an ambient air source, and a pumpingcapacity generated in the common line path by a pressure of thecalibrating gas being higher than a pumping capacity caused by the feedpump.
 9. The method according to claim 6, wherein the calibrating gas ispumped by a pressure at a pumping capacity of about 310 mL/min and theexhaled air or the ambient air is pumped into the common line path at apumping capacity of about 210 mL/min by being driven by the feed pump.10. The method according to claim 2, wherein a purging vessel isprovided along the common line path, the exhaled air flowing throughsaid purging vessel and liquid droplets being removed from the exhaledair.
 11. The method according to claim 1, further comprising,determining, with the gas sensor, a concentration of oxygen in theexhaled air.
 12. The method according to claim 1, further comprising,determining, with the gas sensor, a concentration of carbon dioxide inthe exhaled air.
 13. A device for breath gas analysis, the devicecomprising: a first intake, external to the device, for receivingexhaled air from a subject and for receiving ambient air; a first linepath for the exhaled air and the ambient air, the line path extendingfrom the first intake into the device; at least one gas sensor disposedwithin the device along the first line path; a second intake, externalto the device, for receiving a calibration gas; and a second line pathextending from the second intake into the device, through a valvedisposed within the device, to a portion of the first line path disposedwithin the device, the valve configured to selectively provide thecalibration gas to displace ambient air along the first line path. 14.The device of claim 13, wherein the valve is disposed on the second linepath between the second intake and the first line path.
 15. The deviceof claim 13, further comprising a feed pump configured to pump theexhaled air and the ambient air from the first intake to the at leastone gas sensor.
 16. The device of claim 15, wherein the feed pump isconnected downstream of the at least one gas sensor, the feed pumpconfigured to suck the exhaled air and the ambient air through the atleast one gas sensor.
 17. The device of claim 13, wherein the at leastone gas sensor comprises two gas sensors.
 18. The device of claim 17,wherein the two gas sensors comprise an oxygen sensor and a carbondioxide sensor.
 19. The device of claim 13, further comprising a purgingvessel on the first line path between the first intake and the at leastone gas sensor.
 20. The device of claim 13, further comprising acalibration gas container coupled to the second intake and containingcompressed calibration gas.